Experimental Setup for Co-Cultivation of Model Cyanobacteria with Rice Roots

Co-Inoculation of Rice roots with cyanobacteriaGlass cultivation tubes (Photosystem Instruments, PSI) containing 100 mL BG11 liquid medium were inoculated with Synechocystis sp. PCC 6803 (PCC-M) to an optical density (OD750) of 0.15. Roots of young rice seedlings (variety Kitaake; ~ 1 week after germination) were pulled through the outflow holes of the silicone plugs (PSI) and submerged into the BG11 medium.Co-cultivation took place at ~30 °C, either in a rooftop greenhouse (HHU Düsseldorf, Germany), or in a growth chamber (Versatile environmental test chamber, Sanyo).Note that growth of rice plants is compromised in the latter without humidifier. Leafs were manually humidified with an aerosol. However, cultivation in non-humid environments is not recommended. The co-cultures were supplemented with a continuous stream of air using simple aquarium air pumps. The mass flow was not precisely controlled in these experiment. However, the usage of mass flow control (MFC) devices is recommended. In the growth chamber, co-cultures were constantly illuminated (> 100 µmol m-2 s-1), while greenhouse cultures were subjected to natural day-night cycles (Nov-Jan, Germany, daylight int.: (> 100 µmol m-2 s-1). While the rice seedlings thrived in BG11 medium (buffered to pH 8.0, see link to protocols.io), the tested Synechocystis strains did not proliferate in more acidic medium for rice growth (buffered to pH